1. Field of the Invention
The present invention is a regulator used for regulating fluid pressures in a downstream apparatus. The regulator can also vent overpressures to atmosphere. In addition, an improved bi-directional seal design is used in conjunction with the sliding control stem.
2. Description of the Prior Art
Gilmore Valve Company, the assignee of the present invention, has sold shear valves and other types of regulators for many years. Examples of these prior art devices are shown in U.S. Pat. Nos. 3,917,220 and 4,493,335, both of which are included in the Information Disclosure Statement filed concurrently herewith. In order to adjust the set point for these prior art regulators, the operator was required to turn a large handle at the top of the apparatus which would compress springs on the inside of the apparatus. This was sometimes difficult at higher set points.
Other prior art regulators have adjustment knobs that can sometimes be turned too far, stripping the threads and/or ruining the regulator. A common prior art solution to this problem is anti-rotation pins.
Deadband is a generic term used to describe the envelope of performance when a regulator will not respond to pressure fluctuation. Some prior art devices have deadbands of several hundred pounds. These difficulties and other matters have not been fully addressed by the prior art.
It is known in the prior art to use dual seals in conjunction with each other in order to multiply the sealing force being exerted by one of the seals. For example, in U.S. Pat. No. 3,455,566, a circular o-ring is described as a unit force multiplying seal that exerts pressure on a controlling seal that has a triangular cross-section. Under compression, the shape of the circular o-ring is distorted and additional force is transferred to the second seal. However, this prior art design only works when pressure is applied from a specific direction. There is a need for a dual seal arrangement so that the second seal will function regardless of the direction of pressure that is being applied to the other seal.
Prior art regulators are often difficult to adjust accurately at higher pressures, because the adjustment knob must push against the full force of the sensor piston. In the present invention, the adjustment knob only moves a small diameter control stem. The force on the control stem is sufficient to stabilize the assembly, but requires only minimum adjustment force. The downstream fluid pressure is what moves the sensor piston.
The higher forces and torques of prior art regulators tended to wear out the threads in the adjustment mechanism. The lower forces in the present invention minimize this wear.
There are several types of deadband that describe the performance of regulators. Generally, larger deadbands are less desirable because they degrade the sensitivity of the regulator. Smaller deadbands can also negatively affect durability. Hence, an optimized design balances sensitivity with stability and durability.
The main drive for developing this regulator was an industry demand for more sensitivity of hydraulic regulators in the 1,000 to 10,000 psi range.
If the set pressure is adjusted upward from the forward adjustment set point, until the regulator just starts to supply, then the forward adjustment dead band (sensitivity) is the amount that the pressure increases until it stabilizes.
If the set pressure is adjusted downward from the reverse adjustment set point, until the regulator just starts to vent, then the reverse adjustment dead band (sensitivity) is the amount that the pressure decreases until it stabilizes.
For prior art regulators, both of these dead bands were often larger than 200 psi. The present design has less than a 50 psi adjustment dead band.
Droop dead band is the number of psi that the down stream pressure falls below the forward adjust set point before the regulator starts to supply fluid. Prior art droops were in the neighborhood of 20% of the set pressure. The present design droop is approximately 125 psi, even up to a 9000 psi set pressure.
Accumulation dead band is the number of psi that the downstream pressure increases above the forward adjust set point before the regulator starts to vent fluid. Prior art accumulations were also in the neighborhood of 20% of the set pressure. The present design accumulation dead band is near to 6%.
Prior art regulators tended to chatter or become unstable under certain flow conditions. The present invention has proved to be very stable and quiet due to the soft seat sliding control stem.
The seal is a bi-directional pressure energized seal that allows for a better lower friction seal. The o-ring behind the seal energizes and increases the force through an elastomer seal as differential pressure increases across the seal.
Strong individuals are sometimes known to turn adjustment knobs too hard and strip the threads or ruin prior art regulators. A common solution to this problem in prior art devices is anti-rotation pins. The present invention does not have anti-rotation pins and is believed to have a unique solution to the problem of excess torque. If the adjustment knob on the present invention is turned beyond full open or full closed, it merely causes the internal mechanisms to rotate, rather than strip threads or break.